Why does my scene take longer to render on two modern GPUs, than on CPU?
Oh FFS! There is actually a second switch you have to enable in order for cycles to render on the GPU!

So the answer to why my two Radeon HD 7950 graphics cards where so slow, is that cycles wasn`t using them! It was still rendering on the CPU.  

It is simply not enough to "enable" GPU computing under the Blender User Preferences (Ctrl+Alt+U) -> System -> Compute Device!

What you have to do, to actually render your scene on your GPU is:


Use Cycles to render your scene 
"enable" GPU computing under the Blender User Preferences (Ctrl+Alt+U) -> System -> Compute Device
After this a "Device" option pops up under the "Render" options. Which you have to switch to GPU.


then, and only then, your scene will render on your GPU.

Now that i got this figured out, i have a few follow up questions:

Why is there a second switch for the same option?

Why is the default selection for this option CPU?

Who thought this would be a good idea?